The invention relates to the field of communication networks. More specifically, the invention relates to improving resiliency, scalability, and efficiency in the infrastructure of a network.
The increased popularity of and reliance on the Internet has made the Internet the ultimate computer network. Millions of users around the world access the Internet for personal as well as business use daily. The Internet, however, is not really a specific network at all, but rather an amorphous mass of interconnected networks spanning the globe while utilizing the same Internet Protocol (IP) to pass information from one network to another. The networks making up the Internet are typically arranged in groups of computers connected together to allow information to be transmitted to one another. Such groups are referred to as xe2x80x9clocal area networks (LAN).xe2x80x9d The LAN medium is xe2x80x9cconnectionless,xe2x80x9d i.e., users on the LAN exchange message information without building specific connections to one another. LANs can be connected together to form a larger network (referred to as a xe2x80x9cwide area network (WAN)xe2x80x9d) that may have geographically spaced network members. LANs/WANs that are connected to the Internet are often referred to as xe2x80x9csubnetworksxe2x80x9d or xe2x80x9csubnetsxe2x80x9d of the Internet.
Communication networks and their operations can be described according to the well-known Open Systems Interconnection (OSI) model (also referred to as the xe2x80x9cOSI stack protocolxe2x80x9d) developed by the International Organization for Standardization (ISO). Each of seven layers (i.e., application, presentation, session, transport, network, data link, and physical interface) of the OSI model performs a specific data communications task that provides a service to and for the layer that precedes it (e.g., the network layer provides a service for the transport layer). The operation of the OSI model is often likened to placing a letter in a series of envelopes before it is sent through the postal system. Each succeeding envelope adds another layer of processing or overhead information necessary to process the transaction. Together, all the envelopes help make sure the letter gets to the right address and that the message received is identical to the message sent. Once the entire package is received at its destination, the envelopes are opened one by one until the letter itself emerges exactly as written.
The ISO has specifically defined all seven layers, which are summarized below in the order in which the data actually flows as it leaves its source:
*Layer 7, the application layer, provides for a user application (such as getting money from an automatic bank teller machine) to interface with the OSI application layer. The OSI application layer has a corresponding peer layer in another open system, e.g., the bank""s host computer.
*Layer 6, the presentation layer, makes sure the user information (a request for $50 in cash to be debited from the user""s checking account) is in a format (i.e., syntax or sequence of ones and zeros) the destination open system can understand.
*Layer 5, the session layer, provides synchronization control of data between the open systems (i.e., makes sure the bit configurations that pass through layer 5 at the source are the same as those that pass through layer 5 at the destination).
*Layer 4, the transport layer, ensures that an end-to-end connection has been established between the two open systems and is reliable.
*Layer 3, the network layer, provides routing and relaying of data through the network (among other things, at layer 3, on the outbound side, the xe2x80x9cenvelopexe2x80x9d will be labeled with an xe2x80x9caddressxe2x80x9d which is read by layer 3 at the destination).
*Layer 2, the data link layer, includes flow control of data as messages pass down through this layer in one open system and up through the peer layer in the other open system.
*Layer 1, the physical interface layer, includes the ways in which data communications equipment is connected mechanically and electrically, and the means by which data moves across those physical connections from layer 1 at the source to layer 1 at the destination.
Information transported from network to network on the Internet is done through a system called xe2x80x9cpacket switching.xe2x80x9d All information that is sent or received over the Internet is broken down or disassembled into small portions (referred to as xe2x80x9cpacketsxe2x80x9d) in accordance with a protocol known as xe2x80x9cTransmission Control Protocol (TCP).xe2x80x9d These packets are labeled with address information specifying the destination of each packet, together with an indication of the order in which the packets are to be reassembled at the intended destination. Internet xe2x80x9crouters,xe2x80x9d which join one network to another along the transmission paths of the Internet, are used as path finding devices charged with interpreting the packet labels and determining the best transmission path for a particular packet to take on route to the ultimate destination. On its way to the ultimate destination, the packet will be processed by multiple routers at various points of the Internet. The addressing and routing of the packets conforms with a protocol known as xe2x80x9cInternet Protocol (IP).xe2x80x9d According to the IP, each node of the Internet is provided with a unique IP address having a specific length and format.
Each segment between routers is a point-to-point data transmission referred to as a xe2x80x9chop.xe2x80x9d Although one hop will typically include transmission over a communication line segment connecting one network to another, often a hop will cause a packet to be passed through one or more other network components such as repeaters, hubs, bridges, gateways and switches that are each used by a network to facilitate the transmission of the packets through the network. A repeater, for example, is used to amplify the packet data to extend the distance in which the packet can travel. Repeaters are often found in the dedicated broadband telecommunications connection known as a xe2x80x9cbackbone,xe2x80x9d such as the Internet backbone provided by MCI. (A backbone network (referred herein simply as xe2x80x9cbackbonexe2x80x9d) is a xe2x80x9ctransitxe2x80x9d network often made up of long-distance telephone trunk lines and other wired and wireless links such as microwave and satellite links for use in transmitting large amounts of data simultaneously between host computer systems connected to the Internet. Normal communicated data typically neither originates nor terminates in a backbone network.) A hub is used to tie individual or groups of computers together, controlling the order in which the computers can transmit information to one another. Bridges link LANs together, allowing data designated for one LAN to pass through from one to another. Gateways work like bridges, but also translate data between one network type to another. A switch establishes a connection between disparate transmission path segments in a network (or between networks). A router, which is essentially an intelligent bridge, can be used to control the various path segments connected by a switch based on the destination information contained in the label of a given packet.
Once the transmitted packets arrive at the ultimate destination, the packets are reassembled in proper order by a local server and forwarded to one or more local computers. As with the computer system transmitting the original data packets, the local server is typically connected to the local computers (or terminals) using a direct LAN line, modem dial up, or other well-known connection. As used herein, any computer that is assigned an IP address and connected to the Internet is referred to as a xe2x80x9chost.xe2x80x9d Generally, two types of hosts are present in a system: xe2x80x9cserver hosts,xe2x80x9d which provide services (e.g., web site, e-mail, file access, etc.) to remote computers and terminals; and xe2x80x9cclient hosts,xe2x80x9d which only access services on the Internet provided by server hosts.
Users whose computers and networks are not directly connected to the Internet typically gain access to the Internet through Internet Access Providers (IAPs), Internet Service Providers (ISPs), and Online Service Providers (OSPs) such as Internet MCI. The IAPs, ISPs, and OSPs will collectively be referred to herein as xe2x80x9cInternet providers.xe2x80x9d Internet providers must utilize interface architecture to provide Internet connectivity to their customer users who desire a presence on the Internet. One such known interface architecture is shown in FIG. 4. As shown in dashed outline, hosting center 310 provides the hosting architecture needed to supply customer networks (i.e., xe2x80x9csubnetworksxe2x80x9d or xe2x80x9csubnetsxe2x80x9d) 28a with connectivity to the Internet (represented by Internet backbone 200).
Each customer subnet 28a represents, for example, a LAN (using an Ethernet transmission protocol) and web site server used to supply the content of the customer""s web site as hosted by the Internet provider. Customer subnet routers 36a-36e provide connectivity between the customer subnetworks 28a and the hosting center 310. Information signals to be sent to the Internet from web site servers in the customer subnets 28a are received by the customer subnet routers 36a-36e and converted into the appropriate packets in accordance with the well-known TCP/IP standards required for Internet transmission. The customer subnet routers 36a-36e determine the best path through one of the dual-ring fiber distributed data interface (FDDI) fiber optic networks 34a, 34b (reaching access speeds of 100 Mbs (simplex) per ring) and one of the border routers 32a, 32b. For each data packet routed to border router 32a, border router 32a determines which one of two data service level 3 (DS-3) communication links (30a, 30b), which provide simplex data rates as high as 44.736 Mbps, is the best route to select in order to forward the data packet on its way towards its addressed destination. Similarly, border router 32b determines which one of DS-3 links 30c, 30d is to be selected for data packets border router 32b receives from FDDIs 34a, 34b. 
As the world population increases its computer literacy, the ability to exchange ideas, expressions and discoveries hinges upon the ability of computers and computer systems to interconnect with one another. The recent explosion in usage of the Internet, particularly, the world wide web, as well as the increase in complex, processor-intensive applications intended for use on the Internet, has placed unprecedented demand on computer systems to increase in reliability, capacity and speed. The known interface architecture shown in FIG. 4, for example, was limited to 180 Mbs simplex communications between the border routers 32a, 32b and the Internet backbone 200, and to 200 Mbs around the FDDI networks 34a, 34b. In addition, the architecture is based on two shared physical link protocols: Ethernet and FDDI. As a result, computers and terminals on the Ethernet LAN and routers on the FDDI share a single physical link having a fixed bandwidth. The disadvantage of such protocols is that the addition of more stations on the link reduces the average bandwidth available to each station on the link. Adding customer subnets and routers to satisfy increase in usage, therefore, only adds to the bottlenecks created by the insufficient scalability (i.e., ability to provide adequate solutions with increase in size) of the interface architecture in the hosting center 310.
In addition, the single communication link connecting customer subnet routers 36c and 36d, and the single link between router 36d and 36e presents many single points of failure for customers attached to routers 36d and 36e. The failure along the transmission path between customer subnet routers 36c and 36e would be catastrophic for at least some of these customers. Moreover, because the Ethernet segments connecting the components in the interface architecture must be bridged together in a loop-free topology, redundant paths cannot be created between bridged Ethernet segments. As a result, additional single points of failure of any one of these components in the hosting center 310 would require human intervention to reconfigure the remaining components to bypass the failed component. The lack of resiliency inherent in this architecture contributed to Internet blackouts and slowdowns that occurred often and added delay for data packets to reach their destinations to and from the hosting center.
The invention provides a highly resilient network infrastructure that provides connectivity between a main network such as the Internet and a subnetwork such as a server-based (e.g., web server) local area network. In accordance with the invention, a network interface incorporated into a server hosting center provides a resilient architecture that achieves redundancy in each of three different layers of the Open System Interconnect (OSI) stack protocol (i.e., physical interface, data link, and network layers). For every network device that is active as a primary communication tool for a group of subnetworks, the same device is a backup for another group of subnetworks. Based on the same connection-oriented switching technology (e.g., asynchronous transfer mode (ATM)) found in high-speed, broadband Internet backbones such as that provided by InternetMCI, the network interface architecture provides a high degree of resiliency, reliability and scalability.
In accordance with the invention, interface network routers which provide routing functionality and connectivity between the Internet backbone and the customer subnetworks are fully meshed with those deployed in the Internet backbone. Permanent virtual circuits (PVCs) providing a multitude of logical transmission paths between each hosting center router and every router in the Internet backbone, greatly reduces processing delays of data traffic through the infrastructure as only a single xe2x80x9chopxe2x80x9d routing step is required between any external access point on the Internet backbone and a hosting center router.